Heating device for liquid fuels



Dec. H0), 1935. F. NETTEL HEATING DEVICE FOR LIQUID FUELS Filed May 2,1951 7\TTORN EY Patented Dec. 10, 1935 UNITED STATES PATENT OFFICEApplication May 2, 1931, Serial No. 534,495 In Germany May 2, 1930 2Claims.

Devices for heating of liquid fuels are used for the purpose of internalcombustion engines, furnaces, etc., where vaporizable' particles orvapors suitable for easy mixing with the combustion air are required, orwhere badly combustible or noncombustible components are: to beseparated. Special difficulties are encountered in the conditioning ofhydrocarbons like heavy oil fuels, naphthalineor other fuels of highboiling point,

. alcohols especially, at changing loads.

Known devices to convey the necessary amount of heat to the fuels usehot gases (exhaust or waste gases), heating flames or electric heatingelements which act directly or through heating surfaces.

All these devices suffer, as experience shows, from the disadvantagethat they are not capable of following quick changes in the demand ofconditioned fuel and require complicated regulating devices if automaticaction is required. Strong heating of fuels through heating surfacescauses deposits and coke formation which makes continuous operationimpossible,-open flames or incandescent surfaces cannot be admitted inmany cases, especially in non-stationary plants, because of the firedanger involved in their use.

These disadvantages are avoided in the new device as described herein,which, for the purpose of supplying conditioned fuel for internalcombustion engines or furnaces, uses an internal partial combustioninside of a fuel tank, as known for other purposes, so provided thatoxygen or air led into the tank under an approximately constant butadjustable pressure, higher than the pressure outside the tank, isburned in the vapor, or gas, atmosphere above the liquid level insidethe tank, characterized by the fact that the main part of the contentsof the tank is heated inv liquid state by the combustion heat, and thatthe heating temperature is kept approximately con-- stant by thechanging of the intensity of efflux of the products of the internalcombustion, in definite relation to the desired fuel temperature or therate of discharge of hot fuel from the tank, by hand or automatically bya thermostat or a similar device, in such a way that irrespective of theamount of liquid fuel taken from the tank (while cold liquid isreplacing the hot liquid withdrawn from the tank) the tank contents arekept, automatically, approximately constant at any predetermined, but atwill adjustable, value.

An additional improvement is obtained inpractice by dimensioning thefuel capacity of the tank in such a way that, for the purpose ofsupplying consumers with fluctuating demand, the tank can act ashot-fuel-accumulator.

The usual'fuel supply of internal combustion engines for heavy fuelsrequires very high pump pressure, and the proper ignition and completecombustion makes very high compression of the air charge indispensable.Both measures entailhigh manufacturing cost of the engines and make formachines easily getting out of order and little suitable for high speedoperation. Preheating of 5 fuel is a recognized and known measure. Forlack of suitable heating devices it could up to the present only be usedto av very limited degree, mostly by using exhaust gases as heatingmedium.

Its main object was the improvement of injection condition, but not,which is characteristic of the present invention, the reduction ofcompression. pressure, the speeding-up and improving of combustion,which is obtained by local and timely separation of fuel conditioning,as the case may be, up to loosening of the chemical structure of thefuel molecules, from the formation of combustible mixture and combustionin the consumer (engine or burner).

For this purpose it is important to regulate the temperature of the oil,heated as specified therein, in: such a way that it is injected into thecylinder of the fed engine at a definite temperature irrespective of therate of fuel consumption of the engine.

As the fuel need not be heated further for ignition, or only a little,it does not take heat from the compressed-air to any appreciable degree,and it is possible to design the engine with a relatively lowcompression ratio. The hot fuel jet 39 has also with low excess pressurein the tank sufiici'ent piercing power.

In the accompanying drawing the figure shows an example of the fuelheating device as specified in the present invention for the purpose ofsupplying an internal combustion engine.

a is the fuel conditioning tank bfuel pipe with a float valve connectedto fuel pump supplying cold fuel, the float m resting upon 40 thesurface of the fuel actuating the valve,

c--exhaust pipe for the products of the internal partial combustion withvalve controlled by thermostat m. The thermostat m is affected by thefuel temperature in the tank.

d-intake pipe for ignition fuel of low boiling point for starting theinternal combustion with the assistance of e-electrical ignition device(spark or incan- K descent body) f-oxvsen or air tank under pressurey-burner h-fuel pipe (hot fuel) to the engine cylinder iregulating valvefor compressed air 7cblow-off valve for residue Z--manometer m-float offloat valve b,

nvalve on Fig. 3,

pmanua1 valve on pipe 71.,

r--mdial ribs on tank a.

The startingand operation of the device is' described as follows:

(1) Pumping of fuel into the tank by means of a cold-fuel pump until thefloat valve closes.

(2) Inserting of ignition fuel, for example gas oline, through d, whichsettles above the heavy fuel and saturates the air with its vapors. r r

(3) Switching-in of the'ignition device e, which causes the firstexplosion-like combustion to, T

occur. 7

(4) Gradual 'openingof valve i,'which causes other explosions to followand the tank including its contents is gradually heated. As soon as thefuel is sufficiently hot and the gasoline vapors are replaced by vaporsfrom the heavy fuel, a steadier combustion sets in, which may reach thecharacter of a flame. r

(5) The air inlet is increased by further opening of valve 2' until thedesired. temperature is reached, when the thermostat does the furtherregulation automatically by properly regulating the opening of theexhaust valve and keeps; the temperature constant.

(6) Opening of pipe 72. to the fuel valve of the engine which is nowready to start. The starting of engine is done in the usual way by handor auxiliary power. The automatic regulation which is claimed ascharacteristic for the invention is attained as follows:-- I

If the consumption of fuel increases, the feeding of cold fuel via thefloat valve causes a certain temperature drop, which again affects thethermostat to open pipe e a little more, thus creating a small pressuredrop inside the tank. This again makes for an increaseof air intake andconsequently a more intensive internal combustion, which will last untilthe temperature reaches again its predetermined value, and thethermostat operates in the opposite direction reducing the combustionintensity to its previous value.

In case the fuel consumption drops down to zero the thermostat willclose the pipe c completely; the pressure inside the tank increases inthis case to the same pressure as exists in the compressed air container1, the air intake ceases and the internal flame is extinguished. It willbe seen that it is absolutely impossible for dangerous pressures ortemperatures to arise. At consumption zero, but desired readiness forservice of the device, the extinguishing of the. flame can be preventedby keeping a small opening, for instance, to the atmosphere, in whichcase the opening is adjusted suitably in such a Way that a reducedinternal combustion is main-. tained of such intensity as to cover theunavoidable losses by cooling (convection and radiation). On the otherhand, it may sometimes be desirable to provide for heat radiation andthus slightly lower the temperature of the tank, and for this purposeradial ribs as shown at 1' may be formed or fixed upon the tank. vOnemethod of main? taining combustion when the fuel consumption issubstantially zero is practiced by leaving valve n in pipe slightly openwhen the manual valve p in pipe h is closed. This is of aparticularvalue for internal combustion engines which must be ready to start atany moment, vehicles, boats. etc.

or even a cracking through which the combustion properties are improved.Since, however, the components, liable to be chemically loosened first,are partly unstable compounds, they are proposed to be burned hot instatu nascendi.

'A very valuable use for the heating device as specified herein can bemade by designing part or all of the tank surface as a heat radiatorwith or without ribs for heating the air or other medium in contact withthe exterior surface of 10 the tank. The ribs 1' already mentioned will.

' serve in this capacity. The intensity of the in- .ternal combustioncan be controlled by hand or automatically by the temperature of theambient air or other medium to be heated. A centralized supply of airand cold fuel to any number of stoves makes this systemof centralheating superior to other known systems, because heat losses forstarting and in pipes are avoided and metering of the heat supplied toindividual users, for example in apartment houses, is simplified in sofar as the provision of cold-oil meters is suflicient.

Having now fully described my invention and the manner of using the sameto advantage, 26 I claim: 7

1. In apparatus for heating and feeding liquid fuels including suchsolid fuels as can be liquefied by heating, the combination of a closedtank, means for feeding the liquid fuel into said tank, 30 a constantlevel maintaining means controlling the fuel feed to said tank up to anapproximately constant level, an electrical ignition device operativelypositioned to ignite the fuel in said tank, regulatable means forsupplying a compressed free oxygen containing gas into the tank tomaintain combustion therein by burning part of the fuel content andmaintaining the rest of the fuel content under a pressure aboveatmospheric pressure, a valve controlled outlet for the effiux of theproducts of combustion, a valve controlled outlet for the heated fueland means responsive to the temperature of the heated fuel controllingthe eillux of combustion gases whereby the pressure within said tank,the influx of the oxygen containing gas, and the rate of combustionwithin said tank are varied in accordance with fuel temperature tomaintain the same uniform.

2. In apparatus for heating and feeding liquid fuels including suchsolid fuels as can be liquefied by heating, the combination of a closedtank, means for feeding the liquid fuel into said tank, a constant levelmaintaining means controlling the fuel feed to said tank up to anapproximately constant level, an electrical ignition device operativelypositioned to ignite the fuel in said tank, regulatable means forsupplying a compressed free oxygen containing gas into the tank tomaintain combustion therein by burning part of the fuel content and.maintaining the rest of the fuel under a pressure above atmosphericpressure, means allowing the escape of combustion gases, a valvecontrolled outlet for the heated fuel, means responsive to thetemperature of the heated fuel controlling the efllux of combustiongases, and means for introducing such light fuels into said tank as willform a combustible mixture with the free oxygen containing gas above thefuel level at normal air temperaturein said tank for initiatingcombustion therein. 70

FRIEDRICH NETTEL.

